Evaluates: MAX7349/Emulates: MAX7347/MAX7348
most recent scan code is identified in the
Key Grid
.
Click the
0x04 Configuration
group’s
Read
button
and verify reported status
sound from keypress
.
10) In the
0x05 Ports
group, uncheck the
GPO7
box
and click
Write
. Verify LED2 lights up.
11) In the
0x05 Ports
group, check the
GPO7
box and
click
Write
. Verify LED2 no longer lights.
12) Move shunt JU3 and observe the sounder beep in
response to the ALERT pin. Verify register
0x03
Interrupt
shows ALERT as the source of interrupt.
Click the
0x04 Configuration
group’s
Read
button
and verify reported status
sound from keypress
.
13) In the
Sounder
group, select the sounder com-
mands
125ms
and
C5
from the drop-down menus,
check the
BUF = 0
box, and click
Write
. Verify the
sounder beeps. Click the
0x04 Configuration
group’s
Read
button and verify reported status
sound from keypress
.
Detailed Description of Software
Connecting to Hardware
The software automatically searches for the MAX7349
EV kit hardware when launched. Once the hardware is
found and connected, the I
2
C device address is shown
in the upper-left corner.
Autoread
The software automatically reads registers every 2 to 3
seconds if
Auto Read 1-7
is checked. This option should
be left unchecked when preparing to write new values.
Registers
Each of the MAX7349 registers is represented on the
software’s main window. See Figure 1. Each register has
its own
Read
and
Write
buttons. Clicking
Read entire
FIFO now
reads register 0x00 repeatedly, until the FIFO
indicates that all keypress events have been read.
Key Grid
Whenever a keypress event is received, the key loca-
tion is shown on the
Key Grid
. This grid shows eight
rows and up to eight columns. Register
0x01
Debounce / Port Enable
determines how many of the
column pins are taken away from the
Key Grid
and
used for general-purpose outputs.
Interrupt Response
Although the PC software cannot respond to interrupts
with the speed of a true low-level hardware interrupt, the
software does offer flexibility for evaluation. The software
polls the status of the
INT
output pin every 2 seconds.
The
Interrupt Handler Actions
checkboxes determine
what action the software takes when
INT
is active.
History Window
Each register read or write event is recorded in a scrol-
lable text window underneath the interrupt handler actions.
Keyboard Navigation
When you type on the PC keyboard, the system must
know which control should receive the keys. Press the
Tab key to move the keyboard’s focus from one control
to the next. The focused control is indicated by a dotted
outline. Shift+Tab moves the focus to the previously
focused control. Buttons respond to the keyboard’s
spacebar. Some controls respond to the keyboard’s Up
and Down arrow keys. Activate the program’s menu bar
by pressing the F10 key, then press the letter of the
menu item you want. Most menu items have one letter
underlined, indicating their shortcut key.
Detailed Description of Hardware
The MAX7349 (U1) scans a matrix of keys (KEY0–KEY55).
The evaluation kit provides a 7 x 8 matrix of keys,
although the MAX7349 is capable of scanning an 8 x 8
matrix. To demonstrate general-purpose output capabili-
ty, one of the scanning columns (COL7/PORT7) is con-
nected to an indicator (LED2).
The FTDI FT232BM (U2) provides the USB engine. The
USB 5V power is regulated down to 2.5V by U3. LED1
indicates that USB 5V power is present.
Jumpers JU4 and JU5 optionally disconnect the
MAX7349 SCL/SDA, allowing the use of an external
user-provided I
2
C bus. Jumpers JU9 and JU10 option-
ally disable the on-board 1.5k
Ω
termination resistors R5
and R6, allowing the use of external user-provided I
2
C
pullup resistors.
To optionally improve the sounder output waveform,
space is provided to mount a MAX4366 (U6) and associ-
ated passive components C31–C35 and R21–R25 to form
a lowpass third-order Chebyshev filter and output stage,
as shown in Figure 12 of the MAX7347/MAX7348/
MAX7349 data sheet. If these filter components are
installed, move JU2 shunt to position 2-3 to use the filter
to drive the on-board pizeo transducer.
The low-voltage RISC microcontroller, MAXQ2000-RAX
(U5), processes commands sent by a program running
on the PC. Each particular EV kit has its own custom
software specific to that kit. Connector P5 is used dur-
ing factory tests to program the MAXQ2000 in-circuit
using the JTAG interface. The connector pin configura-
tion is compatible with the MAXQ2000 evaluation kit’s
MAX7349 Evaluation Kit
4
_______________________________________________________________________________________